Add Textual TUI for SkyWalker-1 RF tool

Separate entry point (skywalker-tui) that reuses skywalker_lib.py
unchanged. Five RF modes: spectrum, scan, monitor, lband, track —
each with threaded USB bridge workers for non-blocking I/O.

Includes --demo mode with synthetic signal generation (Gaussian
peaks, noise floor, AGC simulation) for development without hardware.

Custom widgets: spectrum bar chart, rolling waterfall, signal gauge,
sparkline history, transponder table, device status bar.

tui/pyproject.toml

@@ -0,0 +1,24 @@
+[build-system]
+requires = ["hatchling"]
+build-backend = "hatchling.build"
+
+[project]
+name = "skywalker-tui"
+version = "0.1.0"
+description = "Textual TUI for Genpix SkyWalker-1 DVB-S receiver"
+requires-python = ">=3.11"
+authors = [{name = "Ryan Malloy", email = "ryan@supported.systems"}]
+dependencies = [
+    "textual>=3.0",
+    "pyusb>=1.3",
+]
+
+[project.scripts]
+skywalker-tui = "skywalker_tui.app:main"
+
+[tool.hatch.build.targets.wheel]
+packages = ["src/skywalker_tui"]
+
+[tool.ruff]
+target-version = "py311"
+line-length = 100